1. Field of the Invention
The present invention relates to a tone generator, and more particularly, to a tone generator by which the size of a desired tone is memorized to then be varied by an address control. The present application is based upon Korean Application No. 67864/1995, which is incorporated herein by reference.
2. Description of the Related Art
FIG. 1 is a system block diagram of a conventional tone generator. Referring to FIG. 1, a tone read only memory (ROM) 122 converts a tone signal into a digital code by an analog-to-digital(A/D) converter and then stores the same according to a compressive conversion mode of A law or mu (.mu.) law. The tone ROM 122 is installed in a tone generator of a system. An address generator 121 having received an address control signal of a controller (not shown) of the system controls the tone ROM 122 based on the address control signal. Then, the tone ROM 122 reads a tone signal of the corresponding address by the address generator 121 and generates a pulse code modulation (PCM) signal of a desired tone. Then, a serial converter 123 serially converts an input PCM and outputs the same. A tone period control signal generator 124 performed by an external software outputs a tone period control signal. An FET 125 outputs an output signal of the serial converter 123 applied to a drain to an output port of a source using the tone period control signal applied to a gate as a switching signal. Finally, the PCM value output through a switching operation is sent to a codec and is converted into an analog signal to then be heard by a user.
However, the tone ROM 122 should be differed depending on a tone size (frequency combination, tone gain, tone period control signal, number of tone sources, and A/.mu. law, etc.) Further, once the tone ROM 122 is installed, the change of the same is not possible. Also, the tone period control signal generator should be operated by an external software. In addition, the tone ROM 122 should be large.